Individuals who are forced to sit or lie down for extended periods of time typically experience tissue necrosis over localized regions of their body known as decubitus ulcers or pressure sores. In 2009 more than a million people in acute care centers were affected with pressure ulcers. In addition to acute care centers, more than 500,000 people in long-term care centers are diagnosed with pressure ulcers every year. Pressure ulcers generally occur at locations of the body where the bony prominence is high and the underlying skin breaks down when constant pressure is placed against the skin. Blood circulation is inhibited or prevented in these localized areas and can even occur when the patient has been lying against or upon cushioning devices. Examples of areas of the body where pressure sores typically occur include the sacrum, greater trochanter, ischial tuberosity, malleolus, heel, etc. When pressure ulcers form, they can lead to extensive stays in the hospital or even to amputation.
Conventional cushioning devices generally utilize flexible materials such as foam or springs which allow for the cushion to deform and conform to the patient's body. While the cushioning device attempts to redistribute the loading from localized regions of the patient's body to a larger area over the rest of the body, such devices typically bottom out such that the patient's body contacts the underlying platform and nonetheless localizes the pressure onto the body.
Other cushioning devices have utilized fluid-filled cushions which consist of large single bladders or compartmentalized fluid or gas-filled bladders which inhibit fluid contained within the bladders from flowing laterally. In a fluid filled bladder disposed on a contoured seat, the fluid filled bladder typically bottoms out in one or more areas when supporting a patient's body weight. The places where the bladder bottoms out are sources of high localized pressure. Thus, such an assembly does not distribute pressure evenly across the portions of the anatomy in contact with the bladder. The amount of water that is used in such a bladder can be increased such that bottoming out does not occur. However, this design sacrifices stability. Additionally, since such cushions are typically designed to accommodate a wide range of patient populations, patients who are not as heavy as the maximum for which the cushion was designed for will suffer even more lack of stability than would be needed.
Another problem with simply increasing the amount of fluid to prevent bottoming out is that this requires significant volume of fluid beneath the patient and/or require specialized bedding. Additionally, many fluid filled membranes are too thick to provide adequate pressure relief because the hammocking that occurs in the regions of high protrusions. Thus, the suspension of the patient's body typically results in significantly non-uniform pressure application, with higher pressures being applied to protruding portions of the patient's body due to lack of adequate conformance of the bladder material to the patient's body.
Accordingly, there exists a need for a cushioning device which may conform to regions of the patient's body to prevent decubitis ulcers in a manner which is more cost efficient, convenient, and effective.